vhost-user-blk: Device support multiple queues

The previous code only support one queue, and we need
to support MQ in vhost user block device. This patch
can work with SPDK with MQ setting.

Signed-off-by: Yang Zhong <yang.zhong@intel.com>

vm-virtio/src/vhost_user/blk.rs

@@ -64,6 +64,10 @@ impl Blk {
             avail_features |= 1 << VIRTIO_BLK_F_CONFIG_WCE;
         }
 
+        if vu_cfg.num_queues > 1 {
+            avail_features |= 1 << VIRTIO_BLK_F_MQ;
+        }
+
         // Set vhost-user owner.
         vhost_user_blk
             .set_owner()
@@ -95,7 +99,17 @@ impl Blk {
                 .set_protocol_features(protocol_features)
                 .map_err(Error::VhostUserSetProtocolFeatures)?;
         }
+        // Get the max queues number from backend, and the queue number set
+        // should be less than this max queue number.
+        let max_queues_num = vhost_user_blk
+            .get_queue_num()
+            .map_err(Error::VhostUserGetQueueMaxNum)?;
 
+        if vu_cfg.num_queues > max_queues_num as usize {
+            error!("vhost-user-blk has queue number: {} larger than the max queue number: {} backend allowed\n",
+                vu_cfg.num_queues, max_queues_num);
+            return Err(Error::BadQueueNum);
+        }
         let config_len = mem::size_of::<VirtioBlockConfig>();
         let config_space: Vec<u8> = vec![0u8; config_len as usize];
         let (_, config_space) = vhost_user_blk
@@ -113,6 +127,15 @@ impl Blk {
             config.num_queues = vu_cfg.num_queues as u16;
         }
 
+        // Send set_vring_base here, since it could tell backends, like SPDK,
+        // how many virt queues to be handled, which backend required to know
+        // at early stage.
+        for i in 0..vu_cfg.num_queues {
+            vhost_user_blk
+                .set_vring_base(i, 0)
+                .map_err(Error::VhostUserSetVringBase)?;
+        }
+
         Ok(Blk {
             vhost_user_blk,
             kill_evt: None,
@@ -246,7 +269,7 @@ impl VirtioDevice for Blk {
         }
         self.queue_evts = Some(tmp_queue_evts);
 
-        let vu_interrupt_list = setup_vhost_user(
+        let mut vu_interrupt_list = setup_vhost_user(
             &mut self.vhost_user_blk,
             mem.load().as_ref(),
             queues,
@@ -256,25 +279,29 @@ impl VirtioDevice for Blk {
         )
         .map_err(ActivateError::VhostUserBlkSetup)?;
 
-        let mut handler = VhostUserEpollHandler::<SlaveReqHandler>::new(VhostUserEpollConfig {
-            interrupt_cb,
-            kill_evt,
-            pause_evt,
-            vu_interrupt_list,
-            slave_req_handler: None,
-        });
-
-        let paused = self.paused.clone();
         let mut epoll_threads = Vec::new();
-        thread::Builder::new()
-            .name("vhost_user_blk".to_string())
-            .spawn(move || handler.run(paused))
-            .map(|thread| epoll_threads.push(thread))
-            .map_err(|e| {
-                error!("failed to clone virtio epoll thread: {}", e);
-                ActivateError::BadActivate
-            })?;
+        for _ in 0..vu_interrupt_list.len() {
+            let mut interrupt_list_sub: Vec<(Option<EventFd>, Queue)> = Vec::with_capacity(1);
+            interrupt_list_sub.push(vu_interrupt_list.remove(0));
 
+            let mut handler = VhostUserEpollHandler::<SlaveReqHandler>::new(VhostUserEpollConfig {
+                interrupt_cb: interrupt_cb.clone(),
+                kill_evt: kill_evt.try_clone().unwrap(),
+                pause_evt: pause_evt.try_clone().unwrap(),
+                vu_interrupt_list: interrupt_list_sub,
+                slave_req_handler: None,
+            });
+
+            let paused = self.paused.clone();
+            thread::Builder::new()
+                .name("vhost_user_blk".to_string())
+                .spawn(move || handler.run(paused))
+                .map(|thread| epoll_threads.push(thread))
+                .map_err(|e| {
+                    error!("failed to clone virtio epoll thread: {}", e);
+                    ActivateError::BadActivate
+                })?;
+        }
         self.epoll_threads = Some(epoll_threads);
 
         Ok(())

vm-virtio/src/vhost_user/mod.rs

@@ -55,6 +55,8 @@ pub enum Error {
     VhostUserConnect(vhost_rs::Error),
     /// Get features failed.
     VhostUserGetFeatures(VhostError),
+    /// Get queue max number failed.
+    VhostUserGetQueueMaxNum(VhostError),
     /// Get protocol features failed.
     VhostUserGetProtocolFeatures(VhostError),
     /// Vhost-user Backend not support vhost-user protocol.